This invention relates generally to robotic picker mechanisms and more specifically to a robotic picker mechanism for data cartridges for computer information storage libraries.
A computer information storage library (also known as an autochanger) typically includes at least one information storage drive mechanism, a media storage system for computer information media or data cartridges, a picker (also called a manipulator or engagement mechanism) for inserting media or cartridges into drives or storage locations and for extracting media or cartridges from drives or storage locations, and a transport mechanism for moving the picker and media or cartridges between drives and storage. Computer information storage drives with removable media include, for example, disk drives (magnetic and optical) and magnetic tape drives. Media storage systems include, for example, carousels, cylindrical silos, and slotted magazines or racks. There is a wide spectrum of transport assemblies. For example, cartridges may be translated and rotated with four or more degrees of freedom by an anthropomorphic robot arm or cartridges may simply be translated in two dimensions. Alternatively, instead of a separate transport mechanism, the media storage system may be moveable. For example, a carousel may rotate to position a cartridge at a stationary drive. Alternatively, a drive may be moved by a transport system to a stationary cartridge location. There is also a wide spectrum of pickers. For example, friction grippers with multiple fingers may be used, various media or cartridge features may be hooked or clamped, or cartridges may be simply pushed or pulled.
Typically, data cartridges designed for robotic manipulation have catch surfaces, notches or other features on the cartridge shell to facilitate gripping or hooking. Typically, the gripping features are located symmetrically about a central axis to prevent twisting (and possibly binding) during extraction. However, some data cartridges were originally designed for manual manipulation, with no particular features intended for robotic gripping. In particular, the DLT tape cartridge, commercially available from Quantum Corporation, Milpitas, Calif., is of interest for computer information storage libraries, but has few features suitable for hooking by robotic manipulators. The DLT cartridge has a notch in one side wall that is suitable for a hook type gripper, but pulling on only one side may cause the cartridge to twist and possibly bind during extraction. Some gripping mechanisms for the DLT cartridge use friction grippers, typically gripping both cartridge sides. Compared to finger grippers that hook into notches, friction grippers may be relatively complex, leading to higher cost and lower reliability. In addition, friction grippers are sensitive to contaminants or other things affecting the coefficient of friction between the gripper and the surface being gripped.
A drive mechanism may have a latch, handle or door that must be manipulated to insert or remove a medium or cartridge. Sometimes, the drive mechanism may include an automatic powered actuator for a latch, handle or door. If the latch, handle or door is not power actuated, the library picker may need to include an additional capability for manipulating the latch, handle or door on the drive. Drive mechanisms for the DLT cartridge have a handle that is used to align the tape cartridge to reference surfaces and to engage a drive hub. The handle may optionally be power actuated or may be manipulated by a robotic picker. The power actuator adds cost, space and complexity. If multiple drives are used, additional cost, space and complexity is required for each drive. Manipulation of the handle(s) by a picker is desirable to reduce the cost, space and complexity of the library.
There is a need for a finger gripper capable of engaging a single notch on one side of a data cartridge while avoiding binding due to rotation of the data cartridge. In addition, there is a need for a picker capable of manipulating a latch, handle, or door on a drive.
A picker for data cartridges has a sleeve for transporting cartridges, a thumb that is moveable relative to the sleeve and a single finger attached to the thumb. The single finger has an inboard pivot point which results in a self locking action (pulling makes the finger grip tighter), which does not rely on a strong return spring to provide locking force. The finger has an armed state for gripping and a splayed state for release. Switching between states is passive, depending only on one dimensional motion of the thumb relative to the sleeve. The finger has a post that travels in tracks in the sleeve. Switching tracks switches finger states. A spring loaded gate in the tracks enables track switching. Passive gripping and release eliminates the need for multiple drive units or clutch devices for performing the multiple functions of cartridge gripping, cartridge displacement and cartridge release. Potential cartridge wear and binding problems during extraction are eliminated by providing a sleeve guide that limits cartridge rotation, by providing a concave guide surface in storage locations that does not contact the cartridge during the limited rotation, and by proper selection of materials. A corresponding drive has a handle that must be manipulated. The thumb includes details for manipulating the drive handle.